11.2.1 Changing the Mode of the DTrace Helper Device

The DTrace helper device (/dev/dtrace/helper) allows a user-space application that contains DTrace probes to send probe provider information to DTrace.

To trace user-space processes that are run by users other than root, you must change the mode of the DTrace helper device to allow the user to record tracing information, for example:

# chmod 666 /dev/dtrace/helper

Alternatively, if the acl package is installed on your system, you can use an ACL rule to limit access to a specific user, for example:

# setfacl -m u:guest:rw /dev/dtrace/helper

You must change the mode on the device before the user runs the program.

You can create a udev rules file such as /etc/udev/rules.d/10-dtrace.rules to change the permissions on the device file when the system starts.

To change the mode of the device file, the udev rules file should contain the following line:

kernel=="dtrace/helper", MODE="0666"

To change the ACL settings for the device file, use a line such as the following in the udev rules file:

kernel=="dtrace/helper", RUN="/usr/bin/setfacl -m u:guest:rw /dev/dtrace/helper"

To apply the udev rule without needing to restart the system, run the start_udev command.